Mystery of the maya collapse

Mystery of the Maya Mystery of the Maya CollapseCollapse

from Curtis et al. 1997from Curtis et al. 1997 Scientific Authorship: David Hodell & Lisa M. Lixey Scientific Authorship: David Hodell & Lisa M. Lixey

As Interpreted by M. Anderson, 2007As Interpreted by M. Anderson, 2007

Discovery of the MayaDiscovery of the Maya

Maya cities were deserted, hidden by trees, and virtually Maya cities were deserted, hidden by trees, and virtually unknown until rediscovered in 1839 by a rich American unknown until rediscovered in 1839 by a rich American lawyer named John Stevens, who, under appointment by lawyer named John Stevens, who, under appointment by President Martin Van Buren, explored and documented President Martin Van Buren, explored and documented the existence of 44 Mayan sites and cities.the existence of 44 Mayan sites and cities.

Stevens wrote: “ The city was desolate. No remnant of this Stevens wrote: “ The city was desolate. No remnant of this race hangs round the ruins….It lay before us like a race hangs round the ruins….It lay before us like a shattered bark in the midst of the ocean, her mast gone, shattered bark in the midst of the ocean, her mast gone, her name effaced, her crew perished, and none to tell her name effaced, her crew perished, and none to tell whence she came, to whom she belonged, how long her whence she came, to whom she belonged, how long her journey or what caused her destruction…. journey or what caused her destruction….


…….Architecture, sculpture, and painting, all of the arts which .Architecture, sculpture, and painting, all of the arts which embellish, has flourished in this overgrown forest; orators, embellish, has flourished in this overgrown forest; orators, warriors and statesman, beauty ambition and glory have warriors and statesman, beauty ambition and glory have lived and passed away, and none knew that such things lived and passed away, and none knew that such things had been or could tell of their past existence….Here was had been or could tell of their past existence….Here was the remains of a cultivated, polished, and peculiar people, the remains of a cultivated, polished, and peculiar people, who had passed through all the stages incident to the rise who had passed through all the stages incident to the rise and fall of nations; reached their golden age, and and fall of nations; reached their golden age, and perished….perished….


…….We went up to their desolate temples and fallen alters; and .We went up to their desolate temples and fallen alters; and wherever we moved we saw the evidence of their taste, wherever we moved we saw the evidence of their taste, their skill in arts….We called back into life the strange their skill in arts….We called back into life the strange people who gazed in sadness from the wall; pictured them, people who gazed in sadness from the wall; pictured them, in fanciful costumes and adorned with plumes of feathers, in fanciful costumes and adorned with plumes of feathers, ascending the terraces of the palace and the steps leading ascending the terraces of the palace and the steps leading to the temples….overgrown with trees for miles around, and to the temples….overgrown with trees for miles around, and without even a name to distinguish it.”without even a name to distinguish it.”

Links between Links between Climate Climate

Change and Change and Society Society

CollapseCollapse

Our society is increasingly interested in the consequences Our society is increasingly interested in the consequences of future climate and environmental changes, as well as the of future climate and environmental changes, as well as the role that humans play in these changes. role that humans play in these changes.

Human civilizations throughout history have affected the Human civilizations throughout history have affected the environment (and perhaps influenced climate) through environment (and perhaps influenced climate) through deforestation, agriculture, urbanization and industrialization. deforestation, agriculture, urbanization and industrialization.

In turn, climate events such as droughts, floods, and In turn, climate events such as droughts, floods, and hurricanes have impacted ancient cultures, both socially hurricanes have impacted ancient cultures, both socially and economically. and economically.

Copan mound

Maya CivilizationMaya Civilization The Maya civilization is The Maya civilization is

one of the best-known one of the best-known ancient civilizations of ancient civilizations of Mesoamerica. Mesoamerica.

The Maya originated The Maya originated around 2600 BC in the around 2600 BC in the Yucatan peninsula and Yucatan peninsula and rose to a cultural and rose to a cultural and geographical geographical prominence in the prominence in the classic period (250-classic period (250-900 A.D.) when they 900 A.D.) when they occupied present-day occupied present-day Chiapas, Guatemala, Chiapas, Guatemala, Belize, Southern Belize, Southern Mexico and Western Mexico and Western Honduras. Honduras.

Maya CultureMaya Culture By borrowing the ideas and tools By borrowing the ideas and tools of neighboring civilizations, the of neighboring civilizations, the Maya were able to develop Maya were able to develop sophisticated concepts in the sophisticated concepts in the disciplines of astronomy and disciplines of astronomy and mathematics. mathematics.

They used this knowledge to They used this knowledge to construct a calendar system and construct a calendar system and implemented the mathematical implemented the mathematical concept of zero. concept of zero.

The Maya developed a written The Maya developed a written language through the use of language through the use of hieroglyphics and were known hieroglyphics and were known for their ceremonial architecture for their ceremonial architecture that included temple-pyramids that included temple-pyramids and residential palaces. and residential palaces.

The Maya were also skilled The Maya were also skilled farmers, potters, and weavers farmers, potters, and weavers trading and distributing goods trading and distributing goods with distant peoples. with distant peoples.

Copan Great Hieroglyphic Stairway

Maya CultureMaya Culture The Mayan golden age The Mayan golden age lasted five centuries from lasted five centuries from 300 to 800 AD. 300 to 800 AD.

At 800 AD they stopped At 800 AD they stopped building temples, declined building temples, declined and became fragmented and became fragmented in competing states.in competing states.

These were easy prey for These were easy prey for invading forces from the invading forces from the north such as the Toltec. north such as the Toltec.

The Toltecs became the The Toltecs became the ruling elite of the Maya in ruling elite of the Maya in the post classic period. the post classic period. Toltec gods were added Toltec gods were added to the Maya pantheon but to the Maya pantheon but the Toltecs were the Toltecs were absorbed as they leaned absorbed as they leaned to speak Yucatec Maya. to speak Yucatec Maya.

Copan decoration on Temple of Inscriptions

Maya CultureMaya Culture ThThe Maya were organized in e Maya were organized in

city states, sharing the same city states, sharing the same beliefs and deferred to priests beliefs and deferred to priests who derived power from their who derived power from their knowledge of astronomy, knowledge of astronomy, mathematics and numerology. mathematics and numerology.

The Maya were aware of the The Maya were aware of the passage of time. passage of time.

They recorded some dates on They recorded some dates on stelae and probably much stelae and probably much more in books that are lost more in books that are lost now because Spanish Catholic now because Spanish Catholic priests destroyed them to priests destroyed them to eradicate "pagan beliefs". eradicate "pagan beliefs".

To retrace the history of the To retrace the history of the Maya we have to rely on Maya we have to rely on whatever clues we can find in whatever clues we can find in what is left of archaeological what is left of archaeological sites that the Spanish did not sites that the Spanish did not plunder or destroy.plunder or destroy.

Copan

TikalTikal

Deep within the tropical rainforests of Guatemala lies Tikal, Deep within the tropical rainforests of Guatemala lies Tikal, one of the largest cities of the Maya civilization. one of the largest cities of the Maya civilization.

Serving as an administrative, ritual and cultural center for Serving as an administrative, ritual and cultural center for the surrounding urban and agricultural regions, Tikal was the surrounding urban and agricultural regions, Tikal was home to large populations of people. home to large populations of people.

During the time period between 600 and 800 A.D., Tikal's During the time period between 600 and 800 A.D., Tikal's population grew to as many as 60,000 citizens, making the population grew to as many as 60,000 citizens, making the population density of the city several times greater than the population density of the city several times greater than the average city in Europe or America during this time. average city in Europe or America during this time.

Tikal Temple 1

TikalTikal

The city of Tikal occupied a six-square mile area and included as many The city of Tikal occupied a six-square mile area and included as many as 10,000 individual structures, ranging from temple-pyramids to as 10,000 individual structures, ranging from temple-pyramids to thatched-roof huts. thatched-roof huts.

The temple-pyramid was by far the most impressive of the architectural The temple-pyramid was by far the most impressive of the architectural feats and towered above all other structures of the Maya city. feats and towered above all other structures of the Maya city.

Built from hand-cut limestone blocks, the temple-pyramids contained Built from hand-cut limestone blocks, the temple-pyramids contained only one or two narrow rooms and mainly was used for ceremonial only one or two narrow rooms and mainly was used for ceremonial purposes. purposes.

Ancient Tikal © Holdell

TikalTikal

The Maya also built low, multi-room buildings, called palaces, The Maya also built low, multi-room buildings, called palaces, that were thought to have served a residential function for the that were thought to have served a residential function for the ruling class. This palace is also from Tikal. ruling class. This palace is also from Tikal.

Tikal Palace © Holdell

TikalTikal

Tikal Temple of the Masks © Holdell

Maya Cultural PeriodsMaya Cultural Periods The Pre-classic Period: 2000 BC The Pre-classic Period: 2000 BC

to 250 A.D. to 250 A.D. The Classic Period: 250 A.D. to The Classic Period: 250 A.D. to

900 A.D.900 A.D. The Post-classic Period: 900 The Post-classic Period: 900

A.D. to the time of Spanish A.D. to the time of Spanish Conquest beginning in 1524 A.D. Conquest beginning in 1524 A.D.

The Maya culture flourished The Maya culture flourished during the late Classic Period during the late Classic Period from @ 600 to 800 A.D. from @ 600 to 800 A.D.

The Maya Classic Collapse The Maya Classic Collapse civilization occurred between 800 civilization occurred between 800 and 900 A.D. and 900 A.D.

At this time, all of the large At this time, all of the large Classic sites in the southern area Classic sites in the southern area were abandoned, never to be re-were abandoned, never to be re-occupied to the same extent as occupied to the same extent as during the Classic Period. during the Classic Period.

Chart: Coe © 1987

Mystery of the Maya CollapseMystery of the Maya Collapse For over a decade, archaeologists For over a decade, archaeologists

have been trying to unlock the have been trying to unlock the mystery surrounding the collapse mystery surrounding the collapse of the Ancient Maya civilization. of the Ancient Maya civilization.

Did human-induced sociopolitical or Did human-induced sociopolitical or ecological change cause the ecological change cause the collapse of this highly advanced collapse of this highly advanced Mesoamerican civilization, or could Mesoamerican civilization, or could natural climate variability of the natural climate variability of the Yucatan Peninsula have Yucatan Peninsula have contributed to the collapse? contributed to the collapse?

Paleoclimatologists are studying Paleoclimatologists are studying the climatic history of this region to the climatic history of this region to provide archaeologists with the provide archaeologists with the climate context in which the Maya climate context in which the Maya civilization evolved, flourished and civilization evolved, flourished and ultimately collapsed. ultimately collapsed.

Tikal

Mystery of Mystery of Maya Maya

DeclineDecline

The cause of the Maya decline remains their greatest The cause of the Maya decline remains their greatest mystery. mystery.

Their civilization was not destroyed by an overwhelming Their civilization was not destroyed by an overwhelming outside force. outside force.

The Maya power disintegrated from within. The Maya power disintegrated from within. Many hypotheses have been proposed: overpopulation, Many hypotheses have been proposed: overpopulation,

famine, epidemics, civil disorder, or could the common famine, epidemics, civil disorder, or could the common people just stopped believing in the dogma the elites were people just stopped believing in the dogma the elites were using to establish their power and justify their excesses? using to establish their power and justify their excesses?

Copan Popol Nah Council House

Sociopolitical Causes of CollapseSociopolitical Causes of CollapseThe sociopolitical The sociopolitical

causes include: causes include: peasant revolts peasant revolts

resulting in the resulting in the overthrowing of the overthrowing of the elite class elite class

inter-site warfare inter-site warfare between Maya city-between Maya city-states states

invasions by peoples invasions by peoples from outside the from outside the Maya civilization Maya civilization

failure of centralized failure of centralized political authority political authority

Copan sacrificial alter

Natural Causes of CollapseNatural Causes of CollapseNatural causes include Natural causes include

factors such as: factors such as: soil exhaustion due to soil exhaustion due to

slash-and-burn slash-and-burn agriculture agriculture

water loss and erosion water loss and erosion of topsoil evident by of topsoil evident by increased increased sedimentation in lakes sedimentation in lakes

natural disasters such natural disasters such as earthquakes and as earthquakes and hurricanes hurricanes

climatic change climatic change disease disease insect infestations insect infestations overpopulationoverpopulation

Copan Great Ball Court

Natural Causes Natural Causes of Collapseof Collapse

When examining the natural causes that could have incited or When examining the natural causes that could have incited or enhanced the collapse, a further set of both human-induced and enhanced the collapse, a further set of both human-induced and natural climatic factors of the Yucatan Peninsula need to be natural climatic factors of the Yucatan Peninsula need to be considered. considered.

Some scientists theorize that the paleoclimate of the region was Some scientists theorize that the paleoclimate of the region was not only different than the present day climate, but that the not only different than the present day climate, but that the natural climatic variability of the past could have included a natural climatic variability of the past could have included a period of intense drought that occurred at the time of the Classic period of intense drought that occurred at the time of the Classic Maya Collapse. Maya Collapse.

Water deficit on the Yucatan © NOAA

Symptoms of the CollapseSymptoms of the Collapse

Rapid depopulation of the countryside and ceremonial Rapid depopulation of the countryside and ceremonial centers in 50 to 100 years, centers in 50 to 100 years,

Abandonment of administrative and residential structures, Abandonment of administrative and residential structures,

Copan East Plaza with Temple of Inscriptions and alter Q; R: Copan East Plaza and Temple 11 with Popol Nah.

Symptoms of the Symptoms of the CollapseCollapse

Cessation of: building construction, carving of Cessation of: building construction, carving of sculptured monuments, manufacture of sculptured monuments, manufacture of pottery, stonework, jade carvings, Classic pottery, stonework, jade carvings, Classic calendar and writing systems. calendar and writing systems.

Above: Copan temple; Above R: corbeled block-work used by Maya; lBelow R: Copan sculpture.

Yucatan Modern ClimateYucatan Modern Climate Before studying the paleoclimate of Before studying the paleoclimate of

the region, it is important to understand the region, it is important to understand the region's modern climate. the region's modern climate.

Temperature is uniformly warm on the Temperature is uniformly warm on the Yucatan Peninsula with a mean annual Yucatan Peninsula with a mean annual temperature of 25temperature of 25oo C. C.

Precipitation increases from north to Precipitation increases from north to south with minimum values of 500 south with minimum values of 500 mm/yr along the NW coast to a mm/yr along the NW coast to a maximum of 2500 mm/yr in the maximum of 2500 mm/yr in the southern lowlands. southern lowlands.

Rainfall is highly seasonal with the Rainfall is highly seasonal with the rainy season occurring in the summer, rainy season occurring in the summer, May through September, and the dry May through September, and the dry season during winter, October through season during winter, October through April. April.

All of the Yucatan is marked by an All of the Yucatan is marked by an annual water deficit that is lowest in the annual water deficit that is lowest in the southern Yucatan and highest along southern Yucatan and highest along the NW coast. the NW coast. Koeppen Climate classification © NOAAKoeppen Climate classification © NOAA

Lake SedimentsLake Sediments The raw material for The raw material for

paleoenvironmental studies is paleoenvironmental studies is sediment that accumulates in an sediment that accumulates in an ordered manner through time and ordered manner through time and records changes in past climate records changes in past climate conditions. conditions.

The sediments are analogous to a The sediments are analogous to a magnetic cassette tape recording, magnetic cassette tape recording, and the challenge for and the challenge for paleoclimatologists is to "play paleoclimatologists is to "play back" the tape. back" the tape.

Fossil pollen preserved in lake Fossil pollen preserved in lake sediments are often used to sediments are often used to reconstruct vegetation changes reconstruct vegetation changes that can be influenced by climate. that can be influenced by climate.

Sediment core from Lake Chichancanab

Lake Sediment CoresLake Sediment CoresScientists reconstructed the past Scientists reconstructed the past climate of the Maya civilization climate of the Maya civilization by studying lake sediment cores by studying lake sediment cores on the Yucatan Peninsula. on the Yucatan Peninsula. The first area of study, Lake The first area of study, Lake Chichancanab, is located in the Chichancanab, is located in the center of the Yucatan.center of the Yucatan.Lake Chichancanab is a long Lake Chichancanab is a long (26-km), narrow (2 km) lake, (26-km), narrow (2 km) lake, consisting of a series of basins consisting of a series of basins that are connected during high that are connected during high water level. water level.

Jason Curtis holding core form Lake Chichancanab

Lake ChichancanabLake Chichancanab Sediment cores Sediment cores

were collected were collected from the central from the central basin in a water basin in a water depth of 6.9 m. depth of 6.9 m.

The lake lies in a The lake lies in a fault depression fault depression caused by caused by normal faulting. normal faulting. The steep hills The steep hills on the eastern on the eastern side of the lake side of the lake represent the represent the fault line. fault line.

Lake SedimentsLake Sediments Pollen cannot be used to Pollen cannot be used to

reconstruct climate during the reconstruct climate during the Classic Period because the Classic Period because the Maya severely altered regional Maya severely altered regional vegetation through clear cutting vegetation through clear cutting of the forest for agricultural of the forest for agricultural purposes. purposes.

It would be impossible to tell, It would be impossible to tell, whether a given vegetation whether a given vegetation change was caused by climate change was caused by climate or human agricultural activity. or human agricultural activity.

Because of this, scientists rely Because of this, scientists rely upon geochemical (elemental upon geochemical (elemental and isotopic) evidence for and isotopic) evidence for climatic change found trapped in climatic change found trapped in the shells of tiny Crustacea the shells of tiny Crustacea called ostracods. called ostracods.

Oxygen IsotopesOxygen Isotopes One of the most important tools used to One of the most important tools used to

reconstruct the ratio of evaporation to reconstruct the ratio of evaporation to precipitation is oxygen isotopes . precipitation is oxygen isotopes .

Lake water (HLake water (H22O) contains both the light O) contains both the light isotope (isotope (1616O) and heavy isotope (O) and heavy isotope (1818O) of O) of the element oxygen. the element oxygen.

When water evaporates, the lighter isotope When water evaporates, the lighter isotope (H(H22

1616O) evaporates at a faster rate than the O) evaporates at a faster rate than the heavier isotope (Hheavier isotope (H22

1818O) because it has a O) because it has a higher vapor pressure. higher vapor pressure.

The reverse happens when water The reverse happens when water condenses. As long as evaporation equals condenses. As long as evaporation equals precipitation over the lake, the lake is at a precipitation over the lake, the lake is at a steady state and the ratio of steady state and the ratio of 1818O to O to 1616O will O will be constant. be constant.

However, if climate becomes drier and However, if climate becomes drier and evaporation exceeds precipitation, the lake evaporation exceeds precipitation, the lake volume will be reduced and the ratio of volume will be reduced and the ratio of 1818O O to to 1616O in lake water will increase. O in lake water will increase.

Illustration From Curtis, et al © 2007

Oxygen IsotopesOxygen Isotopes Alternatively, under wet climatic Alternatively, under wet climatic

conditions, the lake level will rise and conditions, the lake level will rise and the ratio of the ratio of 1818O to O to 1616O will decrease. In O will decrease. In closed basin lakes, the ratio of closed basin lakes, the ratio of 1818O to O to 1616O in lake water is controlled mainly by O in lake water is controlled mainly by the balance between evaporation and the balance between evaporation and precipitation.precipitation.

The The 1818O to O to 1616O ratio of lake water is O ratio of lake water is recorded by aquatic organisms, such recorded by aquatic organisms, such as gastropods and ostracods that as gastropods and ostracods that precipitate shells of calcium carbonate precipitate shells of calcium carbonate (CaCO(CaCO33). ).

Scientists can measure the Scientists can measure the 1818O to O to 1616O O ratio in fossil shells in sediment cores to ratio in fossil shells in sediment cores to reconstruct changes in reconstruct changes in evaporation/precipitation through time, evaporation/precipitation through time, thus inferring climatic change. thus inferring climatic change.

Illustration © From Curtis, et al © 2007

Hydrology: Closed Basin LakesHydrology: Closed Basin Lakes This study consisted of This study consisted of

taking sediment cores taking sediment cores from two different lakes from two different lakes centrally located on the centrally located on the Yucatan.Yucatan.

Both Lakes Both Lakes Chichancanab and Chichancanab and Punta Laguna are Punta Laguna are considered to be considered to be closed-basin lakes. closed-basin lakes.

The geology of The geology of Yucatan is karst Yucatan is karst (porous limestone), (porous limestone), many of the lakes are many of the lakes are perched above the perched above the water table and water table and isolated hydrologically isolated hydrologically by clay-basin seals. by clay-basin seals.


Closed Basin Closed Basin LakesLakes

Closed-basin lakes have Closed-basin lakes have simple water budgets, and simple water budgets, and typically receive water by typically receive water by precipitation, slope wash, precipitation, slope wash, and groundwater seepage, and groundwater seepage, while losing a majority of while losing a majority of their water through their water through evaporation.evaporation.

Therefore the lake Therefore the lake volume, dissolved solute volume, dissolved solute concentrations and oxygen concentrations and oxygen isotopic ratios are largely isotopic ratios are largely controlled by the ratio of controlled by the ratio of evaporation to evaporation to precipitation.precipitation.

This characteristic makes This characteristic makes closed-basin lakes closed-basin lakes climatically sensitive to the climatically sensitive to the changing conditions of changing conditions of evaporation or evaporation or precipitation. precipitation. Illustration From Curtis, et al © 2007

Oxygen Oxygen Isotope / Isotope / RainfallRainfall

This bar chart shows measurements of the oxygen isotopic ratio This bar chart shows measurements of the oxygen isotopic ratio of modern rainfall and groundwater (blue and magenta) of modern rainfall and groundwater (blue and magenta) compared to lake water from Chichancanab (white) and Punta compared to lake water from Chichancanab (white) and Punta Laguna (yellow). Laguna (yellow).

The results indicate that a significant amount of water received The results indicate that a significant amount of water received by Lakes Punta Laguna and Chichancanab was lost to by Lakes Punta Laguna and Chichancanab was lost to evaporation annually, thereby enriching the lake water in evaporation annually, thereby enriching the lake water in 1818O. O.


Sediment CoresSediment Cores To retrieve sediment cores To retrieve sediment cores

from both lakes, two different from both lakes, two different coring systems were used. coring systems were used.

For the top most sediments For the top most sediments that are water-saturated and that are water-saturated and oozy, a mud-water interface oozy, a mud-water interface corer, consisting of a clear corer, consisting of a clear polycarbonate tube (125 cm polycarbonate tube (125 cm by 7 cm) was used. by 7 cm) was used.

Deeper sections of the core Deeper sections of the core that occur past the mud-water that occur past the mud-water interface are retrieved in 1 interface are retrieved in 1 meter intervals using a meter intervals using a square-rod piston corer. square-rod piston corer.

Similar modified Livingston coring device being used in Trinidad.

Coring Site #2Coring Site #2

The second lake from which scientists retrieved sediment cores was Lake The second lake from which scientists retrieved sediment cores was Lake Punta Laguna, located in the northeastern part of the Yucatan Peninsula Punta Laguna, located in the northeastern part of the Yucatan Peninsula about 20 km N-NE of Coba, a major Mayan archaeological site. about 20 km N-NE of Coba, a major Mayan archaeological site.

Punta Laguna consists of three interconnected basins, each with a Punta Laguna consists of three interconnected basins, each with a maximum depth of about 20-m. maximum depth of about 20-m.

The coring site was located in the far basin in a water depth of about 6.3-m. The coring site was located in the far basin in a water depth of about 6.3-m.

Holdell

Sedimentation RatesSedimentation Rates When the cores are returned to the lab, they are split When the cores are returned to the lab, they are split

in two halves. One-half of the core is sampled and in two halves. One-half of the core is sampled and the other half is archived for future use. the other half is archived for future use.

The core that was sampled from Lake Chichancanab The core that was sampled from Lake Chichancanab had a total length of 4.9 m with a basal radiocarbon had a total length of 4.9 m with a basal radiocarbon age of 9000 years BP. age of 9000 years BP.

The sedimentation rate averaged about 0.5 mm per The sedimentation rate averaged about 0.5 mm per year. year.

The core was sampled continuously at 1-cm intervals The core was sampled continuously at 1-cm intervals over its length. over its length.

A 1-cm sample in the Lake Chichancanab core A 1-cm sample in the Lake Chichancanab core represents about 20 years of deposition. represents about 20 years of deposition.

The sedimentation rate determines the temporal The sedimentation rate determines the temporal resolution of study and as a result, scientists are able resolution of study and as a result, scientists are able to reconstruct climatic changes that lasted for to reconstruct climatic changes that lasted for multiple decades or longer. multiple decades or longer.

The sediments of Chichancanab consisted of The sediments of Chichancanab consisted of alternating layers of organic matter, calcite, and alternating layers of organic matter, calcite, and gypsum. gypsum.

Punta Laguna CorePunta Laguna Core The total core length from Punta The total core length from Punta

Laguna was 6.3m with a basal Laguna was 6.3m with a basal age of 3300 years. age of 3300 years.

The sedimentation rate averaged The sedimentation rate averaged 2 mm/year, which is about four 2 mm/year, which is about four times greater than the times greater than the sedimentation rate in the core sedimentation rate in the core from Chichancanab. from Chichancanab.

A 1-cm sample for the Punta A 1-cm sample for the Punta Laguna core represents only 5 Laguna core represents only 5 years of deposition, permitting the years of deposition, permitting the resolution of much shorter climatic resolution of much shorter climatic events. events.

Sediments in the Punta Laguna Sediments in the Punta Laguna core are composed almost core are composed almost entirely of calcium entirely of calcium carbonate(CaCOcarbonate(CaCO33). ).

Above and previous cores are similar representation taken from recent Trinidad expedition.

Dissolved Dissolved Ions in Lake Ions in Lake

WaterWater

This pie diagram illustrates the dissolved ions in lake water This pie diagram illustrates the dissolved ions in lake water from Lake Chichancanab. from Lake Chichancanab.

It is rather salty with total dissolved solids of 4011 mg/L. It is rather salty with total dissolved solids of 4011 mg/L. Chichancanab in Yucatec Mayan means "little sea", which is Chichancanab in Yucatec Mayan means "little sea", which is

an appropriate name in light of its saline, sulfate-rich waters. an appropriate name in light of its saline, sulfate-rich waters. The dominant anion is sulfate (SOThe dominant anion is sulfate (SO44) and the dominant cation ) and the dominant cation

is calcium (Ca). is calcium (Ca). Chichancanab is saturated for calcium carbonate and is very Chichancanab is saturated for calcium carbonate and is very

close to being saturated for the mineral gypsum (CaSOclose to being saturated for the mineral gypsum (CaSO44). ).

Diagram From Curtis, et al © 2007

Punta Laguna Water ChemistryPunta Laguna Water Chemistry

The water chemistry of Punta The water chemistry of Punta Laguna is quite different from Laguna is quite different from Lake Chichancanab. Punta Lake Chichancanab. Punta Laguna is relatively fresh with Laguna is relatively fresh with total dissolved solids of 835 mg/L. total dissolved solids of 835 mg/L.

The dominant anion is The dominant anion is bicarbonate (HCObicarbonate (HCO33). ).

The lake water is saturated with The lake water is saturated with respect to calcium respect to calcium carbonate(CaCOcarbonate(CaCO33), which many ), which many

aquatic organisms use to form aquatic organisms use to form their shells. their shells.

Lake Chichancanab Core Lake Chichancanab Core ResultsResults

Data from the Lake Chichancanab core supports the Data from the Lake Chichancanab core supports the following interpretation that begins at the base of the following interpretation that begins at the base of the core: core:

From 9200 to 7800 years BP, there was no lake at the coring site as From 9200 to 7800 years BP, there was no lake at the coring site as indicated by the absence of aquatic microfossils and the presence indicated by the absence of aquatic microfossils and the presence of land snails. of land snails.

Beginning at about 7800 years BP, the lake began to fill but the Beginning at about 7800 years BP, the lake began to fill but the salinity was much higher than today. salinity was much higher than today.

Evidence for this includes high sulfur content indicating gypsum Evidence for this includes high sulfur content indicating gypsum precipitation, very high precipitation, very high 1818O and O and 1616O ratios in both ostracods and O ratios in both ostracods and gastropods, and the occurrence of a benthic foraminifera, Ammonia gastropods, and the occurrence of a benthic foraminifera, Ammonia beccarri. beccarri.

Foraminiferas are almost exclusively marine forms but this species Foraminiferas are almost exclusively marine forms but this species can tolerate a wide range of salinity (7 to 67 ppt); however, it only can tolerate a wide range of salinity (7 to 67 ppt); however, it only reproduces between 13 and 40 ppt. The large number of specimens reproduces between 13 and 40 ppt. The large number of specimens of A. beccarri suggests salinities of at least 13 ppt (the modern lake of A. beccarri suggests salinities of at least 13 ppt (the modern lake salinity is only 4 ppt). salinity is only 4 ppt).

Lake Chichancanab Core Lake Chichancanab Core ResultsResults

The lake basin was filled by 7000 years BP, and relatively wet The lake basin was filled by 7000 years BP, and relatively wet conditions prevailed from 7000 to 3000 years BP as evidenced by conditions prevailed from 7000 to 3000 years BP as evidenced by low sulfur, high CaCOlow sulfur, high CaCO33, and low , and low 1818O and O and 1616O ratios of ostracods and O ratios of ostracods and gastropods. gastropods.

Beginning about 3000 years BP, a drying trend began that Beginning about 3000 years BP, a drying trend began that culminated in peak arid conditions between 1300 and 1100 years culminated in peak arid conditions between 1300 and 1100 years BP. BP.

Evidence for climatic drying includes an increase in gypsum (S) Evidence for climatic drying includes an increase in gypsum (S) precipitation and an increase in precipitation and an increase in 1818O and O and 1616O ratios. The peak of this O ratios. The peak of this arid event is well dated by an AMS-arid event is well dated by an AMS-1414C date of a seed taken from C date of a seed taken from the height of the sulfur and oxygen isotope values. the height of the sulfur and oxygen isotope values.

The radiocarbon date of the seed is 1140 +/-35 years BP, which The radiocarbon date of the seed is 1140 +/-35 years BP, which translates to a calendar date of 893 A.D. translates to a calendar date of 893 A.D.

The collapse of the Classic Maya civilization occurred between 800 The collapse of the Classic Maya civilization occurred between 800 and 900 A.D. and 900 A.D.

Data from Lake ChichancanabData from Lake Chichancanab

Oxygen Oxygen Isotope Isotope ResultsResults

This slide compares the oxygen isotope record on the same species This slide compares the oxygen isotope record on the same species of gastropod between the two lake cores: Punta Laguna (above) and of gastropod between the two lake cores: Punta Laguna (above) and Chichancanab (below). Chichancanab (below).

Note that the Punta Laguna record is much higher resolution owing to Note that the Punta Laguna record is much higher resolution owing to higher sedimentation rates than Chichancanab. higher sedimentation rates than Chichancanab.

Within the error of the radiocarbon age models, the period of higher Within the error of the radiocarbon age models, the period of higher mean mean 1818O values in Punta Laguna correlates with the interval of O values in Punta Laguna correlates with the interval of increasing sulfur and oxygen isotope values in Chichancanab. increasing sulfur and oxygen isotope values in Chichancanab.

From Curtis, et al 2007 ©

Punta Punta Laguna Laguna Oxygen Oxygen Isotope Isotope ResultsResults

The oxygen isotope data measured on ostracods from Punta Laguna The oxygen isotope data measured on ostracods from Punta Laguna sediments have been converted from radiocarbon years to calendar sediments have been converted from radiocarbon years to calendar years and compared to Mayan cultural periods. years and compared to Mayan cultural periods.

Superimposed upon the mean changes in the record are distinct peaks Superimposed upon the mean changes in the record are distinct peaks that represent arid climate conditions. that represent arid climate conditions.

These peaks occur at 585 A.D., 862 A.D., 986 A.D., 1051 A.D. and These peaks occur at 585 A.D., 862 A.D., 986 A.D., 1051 A.D. and 1391 A.D. Error is approximately +/-50 years. 1391 A.D. Error is approximately +/-50 years.

From Curtis, et al © 2007

Ostracod Climate DataOstracod Climate Data

From Curtis, et al © 2007

Comparison of Ostracod Data and Comparison of Ostracod Data and Maya Cultural PeriodsMaya Cultural Periods

The first peak at 585 A.D. coincides with the early/late Classic boundary. The first peak at 585 A.D. coincides with the early/late Classic boundary. This boundary is associated with the "Maya Hiatus", which lasted between This boundary is associated with the "Maya Hiatus", which lasted between

530 and 630 A.D. 530 and 630 A.D. The Maya Hiatus was marked by a sharp decline in monument carving, The Maya Hiatus was marked by a sharp decline in monument carving,

abandonment in some areas and social upheaval. abandonment in some areas and social upheaval. This event may have been drought-related. This event may have been drought-related.

From Curtis, et al 2007

Comparison of Ostracod Data Comparison of Ostracod Data and Maya Cultural Periodsand Maya Cultural Periods

During the next 200 years from 600 to 800 A.D., the late Classic During the next 200 years from 600 to 800 A.D., the late Classic Maya flourished and reached their cultural and artistic apex. Maya flourished and reached their cultural and artistic apex.

The next peak in 18O/16O occurs at 862 A.D. and coincides with The next peak in 18O/16O occurs at 862 A.D. and coincides with the collapse of Classic Maya civilization between 800 and 900 A.D. the collapse of Classic Maya civilization between 800 and 900 A.D.

The earliest Postclassic Period was also relatively dry between 986 The earliest Postclassic Period was also relatively dry between 986 and 1051 A.D. At about 1000 A.D., mean oxygen isotope values and 1051 A.D. At about 1000 A.D., mean oxygen isotope values decrease indicating a return to more humid conditions. decrease indicating a return to more humid conditions.

From Curtis, et al 2007

ResultsResults Although a Postclassic Although a Postclassic

resurgence occurred in resurgence occurred in the northern Yucatan, the northern Yucatan, city-states in the city-states in the southern lowlands southern lowlands remained sparsely remained sparsely occupied.occupied.

These findings These findings support a rather strong support a rather strong correlation between correlation between times of drought and times of drought and major cultural major cultural discontinuities in discontinuities in Classic Maya Classic Maya civilization. civilization. Tikal Temple I and Temple II

© Hodell

Climate and Oxygen Isotope Climate and Oxygen Isotope LevelsLevels

This illustration shows the simple working This illustration shows the simple working assumptions for interpreting changes in the assumptions for interpreting changes in the sediment record in terms of climate sediment record in terms of climate (evaporation/ precipitation). (evaporation/ precipitation).

Top: Under conditions of wet climate (low E/P), Top: Under conditions of wet climate (low E/P), we expect high lake levels, dilute concentrations we expect high lake levels, dilute concentrations of solutes, low of solutes, low 1818O to O to 1616Oratios in lake water and Oratios in lake water and aquatic shells, and sediments consisting of aquatic shells, and sediments consisting of mainly organic carbon and calcite. mainly organic carbon and calcite.

Middle: Under conditions of drier climate Middle: Under conditions of drier climate (moderate E/P), we expect lower lake levels, (moderate E/P), we expect lower lake levels, higher concentrations of dissolved solutes, higher concentrations of dissolved solutes, higher ratios of higher ratios of 1818O and O and 1616O, and perhaps O, and perhaps sediments dominated by calcite. sediments dominated by calcite.

Bottom: Under arid climate conditions (high E/P), Bottom: Under arid climate conditions (high E/P), we expect low lake levels (perhaps desiccation), we expect low lake levels (perhaps desiccation), high dissolved solute concentrations, high ratios high dissolved solute concentrations, high ratios of of 1818O and O and 1616O and, in the case of Lake O and, in the case of Lake Chichancanab, sediments dominated by gypsum Chichancanab, sediments dominated by gypsum (CaSO(CaSO44). ).

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